Oxygen analyzer



Dec. 27, 1955 R. D. RICHARDSON 2,728,217

OXYGEN ANALYZER Filed Jan. 10, 1952 Q Q 3 m WYW a OXYGEN ANALYZER Robert 1). Richardson, Michigan City, Ind., assignor to The Hays Corporation, Michigan City, lud., a corporation of Indiana Application January 10, 1952, Serial No. 265,847 8 Claims. (CI. 73-27) This invention relates to improvements in oxygen analyzers and particularly to oxygen analyzers of the type utilizing the paramagnetic properties of oxygen for the purpose of producing a difference in the temperature of two heating elements operating, respectively, in a nonmagnetic field and in a magnetic field. Devices of this character form the subject matter of my co-pending patent applications as follows: Ser. No. 595,569, filed May 24, 1945, now Patent No. 2,658,384 and Ser. No. 762,903, filed July 23, 1947, now Patent No. 2,658,385.

The magnetic properties of gases, and especially the magnetic properties of oxygen, are dependent upon temperature. The magnetic properties decrease as temperatures increase. Because of the variation of the magnetic properties of gases upon variations in temperatures, it is common practice in the art to compensate for temperature variations. The normal method of rendering insensitive to variations in ambient temperatures such devices as gas analyzers or other instruments operating by measuring changes in heat values, or which are so constructed that the value being measured is sensitive to heat changes (such as infrared type gas analyzers), is to place the apparatus or analyzer in a cabinet which is heated and whose temperature is controlled at a value above the temperature of the surrounding air. While this is a simple solution of the problem, it is not adapted to an oxygen analyzer which measures the magnetism of gases because the increase in temperature sacrifices the electrical output or reading secured for any given oxygen concentration. -In other words, the increase in the temperature reduces the sensitivity of the analyzer and reduces its ability to distinguish between small differences in oxygen concentration. There are many instances in which small differences in oxygen concentration are very important or critical, and, consequently, the normal method of compensating for variations in ambient temperature by placing the analyzer in a zone of elevated temperature is not practical. These conditions apply particularly with respect to any hot wire type of analyzer used in the presence of gases having a high thermal conductivity, such as helium or hydrogen.

The primary object of this invention is to provide an oxygen analyzer which operates at a low temperature to secure a high output sensitivity of the analyzer and an ability to distinguish between small differences in oxygen concentration.

A further object is to provide a device of this character wherein a hot wire type of analyzer is employed in a cooling chamber operating at a low temperature under the control of a thermostat and wherein the analyzer is positioned within a bafile chamber within the low temperature zone and isolated from the control thermostat.

A further object is to provide a device of this character wherein a refrigerator chamber has a top opening and receives therein a baflie chamber also having a top opening, which baflie chamber serves to encase a gas analyzer.

nite rates Patent Other objects will be apparent from the following specification.

In the drawings:

Fig. 1 is an assembled view of the device with parts shown in section.

Fig. 2 is a top plan view of the gas analyzer mounted within a baffle chamber.

Referring to the drawing which illustrates the preferred embodiment of the invention, the numeral 10 designates a freezer or refrigerator adapted to operate at low temperatures, and preferably adapted to maintain temperatures at least as low as zero degrees Fahrenheit and, better, still lower temperatures, such as temperatures of 20 F.

The refrigerator 10 comprises the usual housing or casing having a bottom 12 and side walls 14, and which is open at its top. The open top will be provided with a top cover 16. Each of the cabinet walls 12, 14 and 16 is preferably of a hollow construction, having an outer wall-forming panel 18 and an inner wall-forming panel 20, with the space between said panels being filled with insulation material 22. In this respect the construction may be substantially conventional. Refrigerating coils, that is, evaporation coils 24 extend through the side walls 14 in contact with the inner sheath 2i) and constitute heat transfer coils. conduits 26 to a refrigerator compressor unit 28 of any standard and well known type including a drive motor (not shown). An electric power line 30 is connected to the motor of the compressor 28, and electric leads 32 branch from the power line 30 and are connected to a thermostat 34 which is positioned within the cabinet 10 to be responsive to temperature. A controller 36 may be interposed in the lead 32 for the purpose of regulating the temperature to be maintained in the refrigerator. This construction may be standard and, for the use of this invention, any conventional low temperature freezing cabinet and refrigerating system may be employed. this connection it may be mentioned that normal refrigerator controls operating in response to a change of temperature of from two to three degrees Fahrenheit are usable in this invention even though such controls permit swings in the temperature within the chamber, when empty, which amount to as much as 10 F.

Within the refrigerator cabinet 10 I mount a bafile or casing 49, preferably formed of metal and including a bottom panel 42 and side panels 44 and provided with a removable cover 46. The bafile 40 is preferably mounted in an elevated position above the bottom panel 12 by means of legs 48. A handle 49 may be provided to facilitate removal of the cover 46 for access to the interior of the baffle. The bafiie may be of any size found suitable and, while it may substantially fill the casing, all parts thereof should be spaced from the walls of the refrigerator chamber 10, as illustrated, to reduce heat transfer by direct contact. For this purpose the legs 48 may be formed of heat insulating material, if desired.

Within the baflie 49 I position a hot wire type of oxygen analyzer 511 of the construction operating upon the principle disclosed in my co-pending patent applications, Ser. No. 595,569, filed May 24, 1945, now Patent No. 2,658,384, and Ser. No. 762,903, filed July 23, 1947, now Patent No. 2,658,385. This device includes a cell 52 within which are located hot wires. The cell 52 is preferably supported in elevated position within the battle as by means of elongated legs 54. A permanent magnet 56 is mounted pivotally at 58 upon the cell support and has associated therewith a counterweight 60. The arrangement is such that the pole faces 62 of the magnet are positioned to magnetically influence certain pole pieces (not shown) carried by the nonmagnetic cell member 52 at a position to exert a magnetic influence upon gas These coils are connected by' passing into the cell. The conduits 64 lead to the inlet and outlet (not shown) of the oxygen analyzer 50 for the supply of the gas sample whose oxygen component is to be measured. These conduits pass through suitable openings in the baffle and in the refrigerator wall aswill be evident.

The hot wires (not shown) in the cell 52 of the analyzer have connection with an electrical component encased within the housing portion 66 and which may include a Wheatstone bridge and other electrical components. A separable connector 68 serves toconnect electrical leads 70 with the electrical components in the housing 66. The electrical leads 70 will be suitably insulated and preferably form parts of flexible electrical conductors which pass through suitable openings in the baffle 40 and in the refrigerator casing 10 and which lead to a measuring instrument 72 which may constitute either an electrically operating indicator or recorder. Where the device 72 constitutes a recorder, it may have connection with electric powerllines 74.

In the use of the device, assuming that the refrigerator unit 10 has been electrically connected and is operating under control of the thermostat 34 to maintain a desired low temperature and that the source of gas to be analyzed has been connected to the conduit 64 so that gas to be analyzed is supplied to the analyzer 50 and that the measuring instrument or recorder 72 is electrically connected to the analyzer 59 and to a source of power, the

device will be in operating condition. In this condition it is preferred that the top 46 of the bafiie 40 shall be in position and that the top 16 of the refrigerator 10 similarly shall be closed. Of course, it will be understood that for measurement purposes the magnet 56 of the analyzer 50 must be in the position shown with its pole pieces 62 juxtaposed to the cell 52.

In the operation of the device it has been found that the analyzer 50 has a manifold increase in sensitivity as a result of its location in the low temperature atmosphere. Thus tests have revealed that the electrical output of the analyzer 50 is increased approximately tenfold when positioned in an atmosphere of approximately F. as compared to its electrical output when positioned in an atmosphere of normal room temperature, say approximately 70 F. This increase in electrical output is substantially more than could have been predicted by the theory of the magnetism of gases for the hot wire type of magnet analyzer. Higher outputs can be secured when the temperature in the cabinet is dropped at a lower level. In this regard, I have made tests at temperatures as low as F. and I am inclined to believe that the rate at which the electrical output increases is low as the temperature is reduced below 0 F., and that there is no substantial advantage in operating the device at temperatures at or below 20 F. because of the diminishing return and the absence of additional advantage proportional to temperature reduction.

It will be apparent that increases in electrical output of the order above mentioned enhance the sensitivity of the instrument and make possible the operation of the measuring device 72 to read very accurately any small differences in the percentage of oxygen contained within a sample. It is also apparent that the effect of temperature upon the instrument is great and that variations in temperature must be avoided to the greatest extent possible in order to avoid inaccurate readings. As mentioned above, the usual commercial refrigerator controls operate upon diiferences of from 2 F. to 3 F. to start and stop the compressor unit 28, but the lag in the system is usually such that the temperature swings which occur within the chamber of the refrigerator 10 may be as great as 10 F. For example, assuming that it is desired to maintain a temperature of 0 F. and that the control operates on a 2 variation, the control will be set so that it will close the circuit to the motor for the compressor when the temperature reaches 1 F. and will open that circuit to stop the compressor when the temperature reaches 1 F. The lag in the system, however, will usually be such that on a rising temperature within the chamber in which the motor for the compressor is switched on at 1 F., the compressor will not be effective immediately to introduce a temperature lowering factor in the refrigerator, and the chamber temperature may rise as high as 5 F. before it begins to reduce. During reduction, the thermostat will keep the compressor operating until the temperature reaches l R, but the momentum of the refrigerator compressor unit will then be such that refrigerating action will not stop immediately and the temperature will continue to lower until it reaches the neighborhood of 5 F. before a rise in temperature will occur.

It will be apparent that a swing of 10 in temperature in connection with a device which is so highly sensitive to temperature conditions will introduce a substantial range of error in the instrument unless compensationis made. One possibility of such compensation is to change the control so that it is responsive to variations of .approximately one-tenth of one degree Fahrenheit, so as to limit the swing of the temperature of the air within the chamber from 2 F. to 3' F. A control possessing such sensitivity or such reduced tolerance between the opening and closing point for maintaining a steady temperature is a complicated and expensive unit and possesses other disadvantages. I have found that the. use of a baflie 48 will afford substantially the same. or even better temperature steadying effects than occur with an extremely sensitive temperature control. Thus the baflie isolates the analyzer 50 from the variations in temper: ature which occur within the chamber of the refrigerator 10 and maintain the analyzer at a very steady temperature irrespective of the amount of the temperature swing within the refrigerator chamber.

By providing the top openings and the removable top closures 16 and 46, inspection of the device is permitted while in operation without introducing any substantial variation in the indications secured at the instmment 72 due to temperature changes. This results from the efiect of convection flow of air and in this instance prevents any substantial reduction of the temperature within the bafiie 40 because of the trapping of the cold air within the refrigerator chamber and the baflie even when the tops of those parts are removed. In this connection it may be mentioned that the top 46 of the balfie may be omitted completely without substantially altering the operation of the instrument and without subjecting it to fluctuations as temperature varies within the refrigerator chamber 10. It is also possible to operate the device for substantial periods of time without use of the cover 16 upon the refrigerator if that becomes necessary, though some slight sacrifice of accuracy of results may occur.

In the construction of this device the electrical apparatus is preferably made spark-proof throughout by using a sealed thermostat and by enclosing all electrical junctions or contacts in explosion-proof housings. Thisis particularly desirable where the gas being measured is such that an open spark therein would be an explosion hazard. One example of such a use for which this device is especially well suited is for the measurement of the oxygen component present. in hydrogen gas.

Another substantial advantage of this device is that the location of the analyzer in a controlled low temperature renders unnecessary any temperature compensation within the instrument itself, as is sometimes required when the oxygen analyzer is used at room temperature or in atmospheres elevated above room temperature. In, this connection the deflection of the instrument does not change as great a percentage per degree of temperature at the low temperatures as does occur in the usual installations at room temperatures or temperatures above room temperature.

While the preferred embodiment of the invention has been illustrated and described herein, it will be understood that changes in the construction may be made within the scope of the appended claims without departing from the spirit of the invention.

I claim:

1. An oxygen analyzer comprising a refrigerated chamber subject to variations from a predetermined optimum temperature, an oxygen analyzer unit of the type actuated by the paramagnetic properties of oxygen and sensitive to temperature variations, an enclosure within said chamber for receiving said analyzer unit and isolating said analyzer unit from the direct effect of the complete range of temperature variations in said chamber, gas conduits extending to said analyzer from a point exterior thereof, and power leads extending to said analyzer from a point exterior thereof.

2. An oxygen analyzer comprising a refrigerated chamber subject to variations from a predetermined optimum temperature, an oxygen analyzer unit of the type actuated by the paramagnetic properties of oxygen and sensitive to temperature variations, a housing within said chamber and encasing said analyzer unit, means for conducting gas to and from said unit and power leads connected to said unit, said means and leads extending outside said chamber.

3. An oxygen analyzer comprising a refrigerated chamher subject to variations from a predetermined optimum temperature, an oxygen analyzer unit of the type actuated by the paramagnetic properties of oxygen and sensitive to temperature variations, a housing within said chamber for enclosing said analyzer unit and preventing said analyzer unit from sensing the complete range of temperature variations in said chamber, said refrigerated chamber being operable at predetermined temperatures in the range from 32 F. to -20 F., gas inlet and exhaust conduits and power leads each connected to said unit and extending outside said chamber.

4. An oxygen analyzer comprising a refrigerator unit including a chamber, a heat transfer element, a compressor assembly and a thermostat responsive to the temperature in said chamber and controlling said compressor assembly; a housing supported within said chamber to accommodate free air circulation therearound; an oxgen analyzer of the magnetic susceptibility type encased in said housing an electrical measuring instrument located exteriorly of said refrigerator chamber and electrically connected to and actuated by said analyzer, and gas inlet and outlet conduits extending to said analyzer from outside said chamber.

5. An oxygen analyzer comprising a refrigerator unit including a chamber, a heat transfer element, a compressor assembly and a thermostat responsive to the temperature in said chamber and controlling said compressor assembly; a housing supported within said chamber to accommodate free air circulation therearound; an oxygen analyzer of the magnetic susceptibility type encased in said housing an electrical measuring instrument located exteriorly of said refrigerator chamber and connected electrically to and actuated by said analyzer, said thermostat being located externally of said housing; and gas inlet and outlet means connected to said analyzer and extending outside of said chamber.

6. An oxygen analyzer comprising a refrigerator unit including a chamber, a heat transfer element, a compressor assembly and a thermostat responsive to the temperature in said chamber and controlling said compressor assembly; a housing supported within said chamber to accommodate free air circulation therearound; an oxygen analyzer of the magnetic susceptibility type encased in said housing an electrical measuring instrument located exteriorly of said refrigerator chamber and electrically connected to and actuated by said analyzer, said refrigerator chamber and housing each having a top opening and a removable closure for spanning said opening; and gas supply and exhaust means extending to said analyzer from outside said chamber.

7. Apparatus for analyzing a gas to ascertain the oxygen content thereof, comprising a hot wire type of oxygen analyzer sensitive to the efiect of the magnetic properties of the oxygen, means for subjecting said analyzer to a fluctuating sub-freezing atmosphere an enclosure for maintaining the atmosphere immediately adjacent said analyzer substantially constant to avoid variations therein from a predetermined temperature exceeding three degrees Fahrenheit, gas supply and exhaust means, and power leads, said last named means and said leads be ing connected to said analyzer and extending outside of said first named means.

8. Apparatus for analyzing a gas to ascertain the oxygen content thereof, comprising a hot wire type of oxygen analyzer sensitive to the effect of the magnetic properties of the oxygen, a cooler housing said analyzer for continuously subjecting said analyzer to a temperature fluctuating in a selected limited portion of the range from 32 F. to 20 F. means in said cooler for encasing and continuously isolating said analyzer from temperature variations in said cooler, gas supply and exhaust means connected to said analyzer and extending outside of said cooler, and power leads from outside said cooler to said analyzer.

References Cited in the file of this patent UNITED STATES PATENTS 2,482,753 Heineman Sept. 27, 1949 FOREIGN PATENTS 701,478 Germany Jan. 17, 1941 OTHER REFERENCES Research on the Behavior of Paramagnetic Gases in the Non Homogeneous Magnetic Field by Klauer, Turowski and Von Wolff, Berlin, in a Communication from Scientific Lab. of the Auergesellschaft A. G., Berlin, 1941.

A Paramagnetic Oxygen Analyzer by C. A. Dyer, Review of Scientific Instruments, vol. 18, No. 10, October 1947, pp. 696-702. 

1. AN OXYGEN ANALYZER COMPRISING A REFRIGERATED CHAMBER SUBJECT TO VARIATIONS FROM A PREDETERMINED OPTIMUM TEMPERATURE, AN OXYGEN ANALYZER UNIT OF THE TYPE ACTUATED BY THE PARAMAGNETIC PROPERTIES OF OXYGEN AND SENSITIVE TO TEMPERATURE VARIATIONS, AN ENCLOSURE WITHIN SAID CHAMBER FOR RECEIVING SAID ANALYZER UNIT AND ISOLATING SAID ANALYZER UNIT FROM THE DIRECT EFFECT OF THE COMPLETE RANGE OF TEMPERATURE VARIATIONS IN SAID CHAMBER, GAS CONDUITS EXTENDING TO SAID ANALYZER FROM A POINT EXTERIOR THEREOF, AND POWER LEADS EXTENDING TO SAID ANALYZER FROM A POINT EXTERIOR THEREOF. 